Today the majority of the electronic systems are built using different module combinations. The example of such system is the Personal Computer (PC). Its main processor block and main memory are placed on the motherboard, and the additional functional devices (interfaces) are placed on the add-in cards that can be plugged into the female connectors on this motherboard. Such architecture type is very flexible, and systems based on this architecture can be easily customized to fit almost any application.
The modern electronic systems are designed for handling the high speed data traffic between external peripheral devices and main processor. The peripheral devices like HDTV displays, Gigabit Ethernet, Fiber-optic telecommunication require a high bandwidth interface for interconnection between said motherboard (main processor and main memory) and plug-in peripheral interface cards. The PCI express standard defines the new high speed serial interface for device interconnection. To-day the speed of this interface is equal to 2.5 Gbit/sec or 5 Gbit/sec and in the latest revision can go up-to 8 Gbit/sec (for comparison: the original PCI interface uses 33/66 MHz speed).
The PCI express interface includes PCI express Link of dual unidirectional differential Links, implemented as a Transmit pair and a Receive pair. The PCI express Link has to have at least one Lane that represents a set of differential signal pairs (one pair for transmission, one pair for reception). For scale bandwidth of the PCI express interface, a Link may aggregate multiple Lanes denoted by xN where N may be any of supported Link widths. The PCI express specification defines operation for x1, x2, x8, x12, x16 and x32 Lane widths.
For support of this high speed interface the PCI express specification defines the special connectors for the PCI express add-in card and for motherboard. These connectors have different lengths that depend on quantities of said Lanes aggregated in this PCI express Link. At the same time PCI express connector has special means (retention means) for retaining said PCI express add-in card (stabilization) when it is plugged into the PCI express female motherboard connector. These means include Retention Ridge on the connector and “hockey stick” on the PCI express x16 add-in cards.
The PCI express interface is the high speed interface, and the qualitative connection between PCI express add-in card and the motherboard is one of the important parameters that define reliability of computer operation. The mechanical connection is one of the problematic places. The stability of connection resistance and capacitance depend on the immobility of the PCI express add-in card, which is inserted into the motherboard connector, during the operation. Impacts and vibration have an affect on this.
PCI express add-in cards can have the holes (defined by specification) for installing add-in card retainer (bracket) and for fixing PCI express card inside the computer chassis. In addition to the bracket the x16 PCI express add-in cards (with long x16 link connector) have the “hockey stick” that can be held by special retention means placed on the motherboard.
All these standard means that define by PCI express specification can not completely solve the problem of stabilization of said add-in card during operation. The “hockey stick” can be implemented only on x16 PCI express add-in cards. The bracket for holding PCI-express add-in card can not be used in some chassis (for example, a custom made embedded chassis).
There are many different ways how to improve add-in card stabilization inside the motherboard connector.
Many patents denoted to the problem of said add-in card fastening in the connector. It is possible to allocate some groups, using:
1) various types of brackets (U.S. Pat. No. 6,331,940, Wan-Cheng L.) TW248707, U.S. Pat. No. 6,361,343 (Daskalakis G., et al.),
2) “hockey stick” (U.S. Pat. No. 6,672,888, Yueh-Chu K.) or additional tabs on the add-in card (Pat. Appl. US 20040121644, Ling Yun, et al.), U.S. Pat. No. 6,824,413 (Fhipe J., et al.),
3) an additional supporting tab (U.S. Pat. No. 7,255,570, Feldman M., et al),
4) special cartridges surrounding the cards and fastening to main board (Pat. Appl. US 20020109975, Boe G.),
5) special cartridges surrounding the connector (U.S. Pat. No. 6,358,079, N. Scott), and
6) card retainer that presses said card to corresponding connector (U.S. Pat. No. 6,183,284, Gill S., et al), etc.
The devices concerning first three types have similar problems. The devices using cartridges are bulky. The patents: U.S. Pat. No. 6,358,079 (N. Scott), U.S. Pat. No. 6,655,976 (Shipe J. E., et al.), U.S. Pat. No. 6,769,927 (Brewer J.) and U.S. Pat. No. 6,183,284 (Gill S., et al) are most interesting and close to the present invention.
U.S. Pat. No. 6,358,079 (N. Scott) the retention mechanism surrounds the connector located on the base board. It comprises fingers that are located from two sides. These fingers are intended for latching into the notches formed in the add-in card. The offered retention mechanisms of both embodiments are compound and are used together with bracket, and don't exclude possible backlash between surfaces of said fingers and interiors of said notches. The fastening having a similar backlash cannot prevent completely small displacement (wiggling) of the add-in card that in the given patent is took up by a special bracket.
U.S. Pat. No. 6,655,976 (Shipe J. E., et al.) shows a retention clip having a holding post, and its post inserted into and through a hole that is formed on the add-in card. The retention mechanism includes the hook having a downward tapered surface and that is fixed to upright standing body. For its engagement it is necessary that said hook is fallen little bit lower than retention ridge and not press add-in card to female connector. This solution prevents only unplug the add-in card but doesn't prevent wiggling the add-in card inside PCI express female connector during operation.
U.S. Pat. No. 6,769,927 (Brewer J.) represents a variant of a card retention member close to previous patent. A hook placed on the end of said card retention member is movably mounted on the card and must be engaged to the surface of a catch. For this purpose the hook must fall lower than retention ridge and not press add-in card to female connector.
Both of those patents (U.S. Pat. No. 6,655,976 and U.S. Pat. No. 6,183,284) are useless in case if the PCI express female connector has no retention ridge (retention ridge is the optional based on PCI express specification).
U.S. Pat. No. 6,183,284 (Gill S., et al) represents a variant of a card retainer. This solution has very narrow implementation. The space between PCI express female connector and motherboard based on PCI express specification is maximum 1 mm. This makes almost impossible to use this retainer on general motherboard because this space usually blocked by surface mount components (ceramic capacitors, resistors etc.) around the PCI express female connector. At the same time practically it is not possible to make this type of clip because it has to be not conductive and fit under the PCI express female connector (the maximum dimension can be 1 mm by 0.5 mm).
Thus said retention means do not provide simple qualitative connection of high-frequency devices in actual practice conditions.